Gelatin coating compositions



United States Patent GELATIN COATINGv COMPOSITIONS Kirby M. Milton and Thomas F. Murray, Jr., Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed June 4, 1956, Ser. No. 588,951

11 Claims. (Cl. 9694) their hygroscopicit-y. The use of sufiieient of such polyols to improve gelatin compositions such as photographic emulsions at low hurnidities, however, is often prevented because of the formation of undesirable physical and sensitometric properties in the coatings containing them when at high humidities and high temperatures.

One object of our invention is to prepare gelatin coating compositions having improved properties. Another object of our invention is to provide gelatin compositions 'fI0IlI which coatings may be prepared having greatly improved flexibilities over coatings which have been prepared heretofore from. gelatin. A further object of our invention is to provide gelatin coatings which give films which are relatively insensitive to photographic effects of mechanical strain. A still further object of our invention is to provide gelatin compositions containing therein diols' which are free of volatility or hygroscopicity, but which do not decrease inv plasticizing efficiency in the. gelatin under low humidity conditions.

Other objects of our invention will appear herein.

We found that aqueous gelatin compositions provide coatings of greatly improved properties if there are present in those compositions a small amount of a diol of 4-7 carbon atoms, the hydroxyls of which are separated by at least three carbon atoms. Compounds which we 1 have found to be especially useful in this connection are Z-methyl-Z,4-pentanediol; .tanediol and 1,6-hexanediol.

1,5-pentanediol; 1,4-bu- These compounds are found to improve gelatin when present therein in the proportion within the range. of 525.% based on the weight of the gelatin. In proportions of 520% these compounds are found to be effective for reducing the photographic sensitivity of a photographic emulsion to mechanical strain which might be encountered when in the form of sheets or when coated out as a layer. For substantially enhanced plasticization, it is usually desirable that at least 10% of these materials be present in the gelatin and eifective plasticization isobtained in proportions up to at least 25% The gelatin coating compositions may be in the form of aqueous gelatin solutions or they may be in the form of silver halide-gelatin photographic emulsions. These compositions may be coated out onto a surface from which they may be stripped to form a stripping. layer or they may be coated onto a photographic fihn base or onto a photographic paper base to form photographic products. The resulting layers are found to have improved properties as regards either plasticity, -i.e., flexibility or tolerance of mechanical strain or both. In some cases it may be desirable to dry the gelatin coating at a slow rate to obtain the highest flexibility, while in other cases fast drying rates have beenfound togive coatings of superior flexibilities. We have found that the gelatin coating obtained from compositions in accordance with our invention exhibit good flexibility both at low and at high humidity as distinguished from gelatin coatings without added improving agents, or gelatin coatings which contain therein materials which are hygroscop1c such as glycerin or the like.

CASE I Flexibilities in MIT Percent folds Gelatin sheets containing of additive 10% RH. 15% EH.

1 4 1 4 D 0 1 10 1,5-pentane-diol 12 e 13 1,6-hexane-diol 12 I5 l,4butane-diol 6 7 CASE n Percent of Flexibilities Gelatin sheets containing additive in MIT folds 15% RH.

No additive. 2 Glycerin 10 2 D 20 6 20 11 20 13 Flexibilities in MIT Percent folds at 20% R.H. Gelatin sheets and photographic of emulsion sheets containing additive gelatin emulsion sheets sheets 24 14 Glycerin 10 25 22 D 15 39 32 20 54 53 15' 55 53 20 63 74 15' 55' 42 20 66 56 Oftentitnes fl'exibilities depend on the method of drying the gelatin coatings as shown by the following table:

CASE IV Flexibilities in MIT folds at 20% R.H.

Gelatin sheets c0ntaining Skins dried Skins dried for 2 days for 1 hr. at at 70 F. and 120 F. and wet bulb T wet bulb T. of 64 F. of F A. No additive 25- 21 B. 20% pentane-diol 63 19 O. 20% 2-methyl-2,4-pentan 47 127 D. 20% glycerin 54 I 28- These compositions were also coated onto cellulose 3 acetate support and the flexibilities of samples thereof were determined the results being as follows:

Flexibilities in MIT folds at 20% RH.

Cellulose acetate films having gelatin coatings containing- Films dried Films dried at 70 F at 120 F and. 60 F and 75 F wet bulb wet bulb for 1 hour for 35 min A. N additive 6 8 B. 20% pcntane-diol 15 6 C. 20% 2-methyl- 4-pentane-dioL. 14 13 D. 20% glycerin 11 7 Photographic emulsion compositions were prepared having the proportions of additive specified (dry weight of gelatin). These emulsions were coated on to cellulose acetate film base and the ilexibilities of the coated films were tmted, the results being as follows:

Flexibilities in MIT folds at 15% R H.

Cellulose acetate films having photographic emulsion coatings containing- Films dried Films dried at 67 F. and at 110 F.

wet bulb and wet bulb T. of 60 F. T. of 70 F.

for 1 hour for 1% min.

A. No additive 5 0 B. 20% pentane-diol 15 1 3o 0. 20% 2-methyl-2,4-pentane-diol 14 19 D. 20% glycerin. 14 0 The following examples illustrate the invention:

Example 1 Gelatin sheets were prepared from solution containing 8% of photographic gelatin and the indicated amounts of improvement agent. These solutions were coated out onto plates from which they could be readily stripped in such volume that the coatings had a dried thickness of 4 mils. The sheets were cured at 70 F. and 70% relative humidity until dry. They were then stripped from the plates, slit to widths of 15 mm. and conditioned at 70 F. and 20% relative humidity. Their folding endurance was tested by an MIT fold tester using a tension of l kilogram and jaws of 0.0155inch radius of curvature with a separation of 0.01 inch. The following 'results were obtained:

Percent Additive 71 1,5-pentane- 74 1,6-hexane-diol 69 1,3-butane-diol 62 2,5-hexane-diol 59 Example 2 A series of sheets were prepared as described in the preceding example using the amounts of improvement agent indicated below. The sheets obtained were tested and the results obtained were as follows:

The presence of the diols of our invention causes a marked reduction in the adverse photographic efiect resulting from physical stresses applied to the silver halide gelatin emulsion layer containing them. The benefit is illustrated in the following two examples:

Example 3a To separate portions of a panchromatically sensitized gelatin-silver-brornoiodide emulsion were added respectively:

(a) 13 g. glycerin per mole of silver (b) 10 g. 2,2-dirnethyl-1,3-propanediol per mole of silver (c) 10 g. 2-methyl-2,4-pentanediol per mole of silver Each sample was coated on a cellulose acetate support. Two strips from each of these coatings were equilibrated at 70 F. and 50% relative humidity for 3 hours. To one of these strips from each coating tension was applied at a constant rate of elongation until 8% elongation was obtained, at which point the tension was released. All strips were then given identical step wedge exposures to light and developed in Kodak Developer DK-SO for 5 minutes at 68 F.

The effect on developed density resulting from the elongation stress was measured at an exposure which yielded a density of 0.8 in the unstretched control strip in each case.

In the strip containing glycerin, the elongation stress resulted in a 0.14 (approximately 18%) reduction in density. There was no density loss resulting from stress with the strip containing 2,2-dimethyl-1,3-propanediol and only 0.04 (5%) density loss with that containing 2- h iAt exposure which gave a density of 0.8 in the unstressed control sps.

Example 3b Similarly, glycerin and 1,5-pentanediol were added to separate portions of a fast negative emulsion. The emulsions were coated and handled in the same manner as in Example 3a. Elongation stress resulted in very much less density and speed loss with the coating containing 1,5-pentanediol as is shown in the following table:

Percent Relative Additive Elongar Speed Density tion Glyce i g 28 w 1,5-Pentauediol g 3% 613g t:{At exposure which gave a density of 1.0 in the unstressed control The photographic emulsions used in practicing our invention are generally of the developing-out type; also, it is to be understood that photographic emulsions of vary ing halide content can advantageously be used.

The emulsions can also be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added such as those described in Sheppard US Patent 1,574,944 and US. 1,623,499, and Sheppard and Brigham US. Patent 2,410,689.

The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to group VIII of the periodic table of elements and have an atomic Weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts as described in Waller and Dodd U.S. Patent 2,399,083 or stabilized with gold salts as described in Damschroder U.S. Patent 2,597,856 and Yutzy and Leermakers U.S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents such as stannous salts (Carroll U.S. Patent 2,487,850), polyamines such as diethylene triamine (Lowe and Jones U.S. Patent 2,518,698), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925), or bis-(fl-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U.S. Patent 2,521,926).

The emulsions can also be stabilized with the mercury compounds of Allen, Byers and Murray U.S. Patent 2,728,663, Carroll and Murray U.S. Patent 2,728,664, and Leubner and Murray U.S. Patent 2,728,665, the tetrazaindenes of Carroll U.S. Patent 2,716,062, and the quaternary benzothiazolium compounds of Brooker and Stand U.S. Patent 2,131,038.

The emulsions may also contain speed-increasing compounds of the quaternary ammonium type of Carroll U.S. Patent 2,271,623, Carroll and Allen US. Patent 2,288,- 226, and Carroll and Spence U.S. Patent 2,334,864, and the polyethylene glycol type of Carroll and Beach U.S. Patent 2,708,162.

The plasticizing agents and other addenda which we have described may be used in various kinds of photographic emulsions. In addition to being useful in nonoptically sensitized emulsions they may also be used in orthochromatic, panchromatic and X-ray emulsions. They may be added to the emulsion before or after any sensitizing dyes which are used. Various silver salts may be used as the sensitive salt such as silver bromide, silver iodide, silver chloride or mixed silver halides such as silver chlorobromide or silver bromiodide. The agents may be used in emulsions intended for color photography, for example, emulsions containing colorforming couplers or emulsions to be developed by solutions containing couplers.

The dispersing agent for the silver halide may be gelatin or other colloidal material such as collodion, albumin, cellulose derivatives or synthetic resins.

We claim:

1. An improved gelatin composition predominantly consisting of an aqueous solution of gelatin containing therein 5-25%, based on the weight of the gelatin, of a dihydroxy alkane which contains, except for the hydroxyl groups therein, only hydrogen and 4-7 carbon atoms, the hydroxyls of the dihydroxy alkane being separated by at least 3 of the carbon atoms.

2. An improved gelatin composition predominantly consisting of an aqueous solution of gelatin containing 6 therein 10-25%, based on the weight of the gelatin, of a dihydroxy alkane which contains, except for the hydroxyl groups therein, only hydrogen and 4-7 carbon atoms, the hydroxyls of the dihydroxy alkane being separated by at least 3 of the carbon atoms.

3. An improved gelatin composition predominantly consisting of an aqueous solution of gelatin which contains 5-25%, based on the weight of the gelatin, of 1,5- pentanediol.

4. An improved gelatin composition predominantly consisting of an aqueous solution of gelatin which contains 5-25%, based on the weight of the gelatin, of 1,4- butanediol.

5. An improved gelatin composition predominantly consisting of an aqueous solution of gelatin which contains 5-25%, based on the weight of the gelatin, of 1,6- hexanediol.

6. An improved gelatin composition predominantly consisting of an aqueous solution of gelatin which contains 5-25%, based on the weight of the gelatin, of 2- methyl-2,4-pentanediol.

7. A gelatin-silver halide photographic emulsion predominantly consisting of silver halide in an aqueous solution of gelatin containing 5-25%, based on the weight of the gelatin, of a dihydroxy alkane which contains, except for hydroxyl groups, only hydrogen and 4-7 carbon atoms, the hydroxyls of the dihydroxy alkane being separated by at least 3 of the carbon atoms.

8. A gelatin-sliver halide photographic emulsion predominanly consisting of a silver halide and an aqueous solution of gelatin containing 5-25%, based on the weight of the gelatin, of 1,5-pentanediol.

9. A gelatin-silver halide photographic emulsion predominantly consisting of a silver halide and an aqueous solution of gelatin containing 525%, based on the weight of the gelatin, of 1,4-butanediol.

10. A gelatin-silver halide photographic emulsion predominantly consisting of a silver halide and an aqueous solution of gelatin containing 5-25%, based on the weight of the gelatin, of 1,6-hexanediol.

11. A gelatin-silver halide photographic emulsion predominantly consisting of a silver halide and an aqueous solution of gelatin containing 525%, based of the weight of the gelatin, of 2-methyl-2,4-pentanediol.

References Cited in the file of this patent UNITED STATES PATENTS 1,757,482 Seel May 30, 1930 2,009,029 Sly July 23, 1935 2,364,017 Baldsiefen Nov. 28, 1944 2,441,389 Blake May 8, 1948 2,477,742 Hall Aug. 2, 1949 2,606,124 Schmutzler Aug. 5, 1952 2,616,812 Kramskey et al. Nov. 4, 1952 2,629,659 Mueller Feb. 24, 1953 2,704,269 Tice Mar. 15, 1955 2,870,062 Stanley et al. Jan. 20, 1959 OTHER REFERENCES Doolittle: The Technology of Solvents and Plasticizers, page 673, John Wiley & Sons, Publ. NY. (1954). 

1. AN IMPROVED GELATIN COMPOSITION PREDOMINANTLY CONSISTING OF AN AQUEOUS SOLUTION OF GELATIN CONTAINING THEREIN 5-25%, BASED ON THE WEIGHT OF THE GELATIN, OF A DIHYDROXY ALKANE WHICH CONTAINS, EXCEPT FOR THE HYDROXYL GROUPS THEREIN, ONLY DIHYDROXY ALKANE BEING SEPARATED BY 1% AND VANADIUM UP TO A MAXIMUM OF 1%, THE BALANCE AT LEAST OF THE CARBON ATOMS. 